1. Field of the Invention
The present invention relates to a method of mutually connecting aluminum alloy die cast members, further specifically, to a method of simply and strongly connecting a plurality of aluminum alloys molded as a die cast member while maintaining the molded shape of the alloy.
2. Description of Related Art
Aluminum alloy die cast members are suitable when parts having a relatively simple shape are molded in large amount, and for obtaining parts having a relatively complicated shape in large amount, it is desirable that aluminum alloy die cast members molded in simple shape are mutually connected by a simple means.
However, in the case of this mutual connecting of aluminum alloy die cast members, these die cast members are previously molded into desired shape, therefore, it is necessary to use a method causing no deformation of parts by partial melting of connecting surfaces while maintaining the shape thereof in connecting, or a method capable of correctly prospecting its deformation amount to a certain degree, and capable of performing simple connecting. Unless such a method is not used, when, for example, die cast members having grooves in the form of semi-cylinder on a connecting surface are to be mutually connected to form cylindrical pores between connecting surfaces by these grooves in the form of semi-cylinder, cylindrical pores are not obtained due to deformation between connecting surfaces, and even if the members are connected, they cannot be used sufficiently.
As a method which can be utilized for connection of such members, there are conventionally known methods such as, for example, spot welding, upset butt welding, pulse energizing connection and the like, however, in these methods, connecting surfaces in mutual contact under pressure are partially melted and connected in a short period of time, consequently, a merit of short connecting time is provided, however, since deformation is generated by melting at welding parts of members to be connected, this is not necessarily suitable as a method for connecting a plurality of aluminum alloys molded as a die cast member while maintaining the molding shape of the alloys.
Further, in an aluminum alloy molded as a die cast member, a chemically stable surface oxide membrane Al2O3 is formed on its surface and it constitutes a disturbance against connection, therefore, in connecting members, it is necessary that the membrane is removed mechanically or metallurgically and the members can be connected strongly by a simple means.
As the method for removing this surface membrane and effecting stable connection, a technology as disclosed in Japanese Patent Application Publication (JP-B) No. 5-62034 has been previously developed. Japanese Patent Application Laid-Open (JP-A) No. 2002-35955 discloses a technology for heating connecting surfaces simply.
Further specifically, in the method of connecting aluminum and the like disclosed in the patent document No. 5-62034, aluminum or aluminum alloy containing 0.2 to 3 wt % of magnesium is allowed to intercalate between connecting surfaces, and the connecting surfaces are pressed and heated at the diffusion temperature of magnesium in a high vacuum atmosphere (10−5 Torr), thereby diffusing magnesium at the connecting interface, and the connecting surfaces are tried to be connected strongly by reduction of the oxide membrane by magnesium.
Further, in the method of producing an aluminum alloy die cast member disclosed in JP-A 2002-35955, connecting surfaces of members to be connected are subjected to processing such as grinding, polishing and the like to give a rough surface having a surface roughness (maximum height Ry) of 30 to 200 μm, and clean connecting surfaces are mutually contacted and electric current is applied through along a direction perpendicular to the connecting surface to generate heat by resistance and the connecting surfaces are connected under pressure, wherein the heating temperature in applying electric current is 400 to 500° C. and the pressure at the connecting surface is 10 to 50 MPa. It is also described therein that a metal powder can be distributed smoothly on concave portions of a rough surface.
The method of patent document 5-62034 suggests a technology effective for removing an oxide membrane by the reducing action of magnesium to enhance connection strength, however, JP-B 5-62034 does not suggest connecting a plurality of aluminum alloys while maintaining its molded shape, additionally, the technology of JP-B 5-62034 is not suitable for simple connecting on die cast members produced in large amount, since it is necessary to heat for a long period of time while pressing in a high vacuum atmosphere (10−5 Torr).
Further, the method of JP-A 2002-35955 has a main object of performing connecting of high strength at low temperature by conducting effectively partial heating of connecting surfaces by energizing heating utilizing irregularity of the connecting surfaces, and does not remarkably consider removal of the oxide membrane.